// GET /api/themes (stream S4, PLAN C5): the installed, valid colour themes, found by listing
// packages/plugins/theme/ on each request, so removing a module's directory takes its theme
// out of the answer at once and putting it back returns it. The answer is data the Settings
// picker and the page's theme code use: { themes: [{ id, displayName, tokens }] } with tokens
// { light, dim, dark } of #rrggbb values, checked by plugins/src/theme.mjs. A module that is
// refused is not in the answer; the refusal goes to the Console's log, once per distinct reason
// so a poll does not repeat it. Nothing here reads a request body, a header or a query.
import { installedThemes } from '../../plugins/src/theme.mjs';

const json = (res, status, value) => { res.writeHead(status, { 'content-type': 'application/json', 'cache-control': 'no-store' }); res.end(JSON.stringify(value)); };

export async function themesHTTP(req, res, { log = () => {}, list = installedThemes, seen = themesHTTP.seen } = {}) {
  if (req.method !== 'GET') return json(res, 405, { error: 'method not allowed' });
  try {
    const { themes } = await list({
      log: entry => {
        const key = `${entry.name}\0${entry.code}\0${entry.message}`;
        if (seen.has(key)) return;
        seen.add(key);
        log(`${new Date().toISOString()} theme refused name=${JSON.stringify(entry.name)} code=${JSON.stringify(entry.code)} message=${JSON.stringify(entry.message)}`);
      },
    });
    return json(res, 200, { themes: themes.map(({ id, displayName, tokens }) => ({ id, displayName, tokens })) });
  } catch (err) {
    log(`${new Date().toISOString()} theme list failed error=${JSON.stringify(String(err?.message ?? err).slice(0, 200))}`);
    return json(res, 500, { error: 'themes-unavailable', message: 'the installed themes could not be read' });
  }
}
// What this process has already logged; a test passes its own set.
themesHTTP.seen = new Set();